understand that air can be dirty, even if this can not be seen know some of the key terms associated with air pollution.

Resources needed:

Professor's letter 1

Scientists notebook (1 copy per child)

Professor's letters 2 and 3

Blank paper / coloured pencils (for the poster task)

Segment 1: What do good scientists do?

Explain to children that you have received a mysterious letter (Professor's letter 1). Give it to one of the children and invite him/her to read it aloud to the rest of the class. Discuss the professor's mission with the children. What do they think would make someone a good scientist? List their ideas on the board. Hand out copies of the scientists notebook, and ask children to examine it in pairs. What can they see which is wrong? Have them make notes and annotations about this onto the document.

Bring the group back together and ask them to identify the problems they noticed, and suggest what the scientists should have done instead. (See 'notes' section for suggestions of the kinds of things they might say.) Review the 'what would make a good scientist' list and add any new ideas which have come out of this discussion.

Poster task:

From the brainstorm, or using ideas of their own, ask children to identifythree things they will pledge to do. Have them finish the sentence : 'As a citizen scientists, I will....' and turn their pledge into a poster for display at the parent meeting and then at home.

Whole class / mini plenary -

Ask some children to share their pledges with the rest of the class. Compare similarities and differences.

Segment 2: Invisible dirt

Tell the class that you have another letter from the professor which you're not supposed to share with them yet, but because you're so impressed with their pledges you think that it would probably be OK. Read Professor's Letter 2 to them or have one of the pupils read it.

Discuss the professor's 'sensitive issue' and the riddle he has posed. How is a human similar to a car? Discuss this, drawing parallels between food giving us energy which causes waste (including gas) and cars using petrol for energy, giving off waste products from their exhaust pipe.

Read Professor's Letter 3 to the class and show them Concept Cartoon 1. Ask children which scientist they think is right. Do they know already, or are they guessing? Remind them that good scientists rely on data – sometimes this is data they collect, sometimes it comes from a secondary source.

Pair work :

Give children the clean air fact sheet and ask them to mark the information which supports their opinion. Ask again, and have them justify their answer with information from the text. Discuss two types of invisible pollutants, N02 and particulates.

Optional plenary session:

If time allows, play ‘Clean Air Bingo’ as a whole class activity. Children make their own bingo sheets by folding a sheet of paper into a 4x4 grid and writing one term in each square. Read out a definition, and have children cross off the matching term.

The Children of Corpus Christi SchoolTrent Road London SW2 5BL3 March 2015

Dear Citizens,

I am writing to seek you help with an urgent matter. For some time now, I have had a team of scientists working for me, on a problem which is of utmost importance to the people of Tulse Hill.For reasons that I won't bore you with, I suddenly find myself with no staff. To be honest, I'm glad to be rid of a few of them, as their work was very poor. (Also, they are all very lazy. I have been trying to get them to do more exercise, but they don't seem to be listening.) Even so, the fact remains that I still have work to do, and no scientists to help me. I also have a whole cupboard full of brand new equipment which they were going to use, but which is now gathering dust.

It has been brought to my attention that you, the children and families of Corpus Christi school, may be able to help me. Personally, I am not convinced. It is bad enough to expect ordinary citizens to do the work of scientists. But children working as scientists? Is that really a good idea?I am, however, somewhat desperate. So I am willing to give you a chance. However, before I can trust you with my equipment, you'll have to prove your worth.

I'd like you to come up with a Citizen Scientists Pledge, describing the way you plan to work. I'm not going to tell you what should be in your pledge, because good scientists should know that for themselves. However, I enclose a copy of a page from a notebook left behind by one of my scientists. Do you remember that I told you some of them were below par? Well, this one was one of the worst. You would be advised to study his notes closely, and avoid making the same mistakes.

The Children of Corpus Christi SchoolTrent Road London SW2 5BL3 March 2015

Professor's Letter 2

Dear Citizen Scientists,

Very well. It seems that yours are the sorts of scientific minds I need. Perhaps we will be able to work together after all. I will arrange for the equipment you need to be distributed to you and your parents later this week.Meanwhile, I need your help with a slightly delicate matter, to do with my diet. Here is what I ate yesterday:Breakfast: scrambled eggs (6) on toast. Mid morning snack: 3 pickled eggs. Lunch: egg fried rice with a side dish of egg salad. Dinner: cheese omelette (made with 4 eggs). Dessert: Cadbury Creme egg.

What can I say? I like eggs. The problem is, they make me........ well, digesting all of those eggs makes a lot of gas, and that gas has to go somewhere. I am sure you can imagine the rest. Let's just say my office doesn't smell too good, most of the time. Which got me thinking about how clean the air in there is..... and that's why I have a problem.

But before I tell you about that, I have a riddle for you: How is a car like a human body?Read my next letter once you have worked out the answer. If you're smart enough to work it out, perhaps you'll be smart enough to solve my problem.

Yours sincerely, and with great eggs-pectations,

The Professor

P.S Perhaps if you have enough time, you could also find out how healthy it is for me to be eating so many eggs. I've been eating nothing but eggs for so long now, I've almost forgotten what else I like to eat. Could you suggest a healthy meal plan for the week?

The Children of Corpus Christi SchoolTrent Road London SW2 5BL3 March 2015

Dear Citizen Scientists,

Did you solve my riddle? Egg-cellent! Yes, just like human bodies need food for energy, cars need fuel to keep them going. And just like humans, once they've converted all of that fuel, there is some waste to get rid of. That's why cars have exhaust pipes.

Have you ever noticed the nasty gas which comes out of cars? After all, you're exactly the right height to spot it. It looks a bit like smoke, especially if the car isn't working well or is getting a bit old.So sometimes we can smell that the air isn't clean, and sometimes we can see that it isn't clean. Which brings me to my problem. INVISIBLE DIRT. Does it exist?

Let me explain. Not all of my old scientists were rubbish. Some of them were quite brilliant. I heard two of them talking last week, but I couldn't see their faces, so I couldn't work out if they were the clever scientists or the rubbish ones. They were having a disagreement with each other so, in fact, there must have been one of each.Anyway, I'm enclosing a cartoon I drew of them. Have a look and see what you think. Who should I believe?

Yours sincerely,

The Professor

P.S. If it turns out that there ARE things which make the air dirty, but which we can't see, how on earth are we going to measure them? I think I might need to pay a visit to my inventor friend.......